JPH0626311U - High frequency oscillator - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a high-frequency oscillator circuit capable of reducing the emission of harmonic signals without mounting a shield case. [Structure] A high-frequency oscillation circuit is configured using the bipolar transistor 11, and a band elimination filter 20 having an oscillation target frequency as a center frequency is connected between the base and collector of the bipolar transistor. The waveform of the base signal and the waveform of the collector signal of the bipolar transistor have opposite phases, and the frequency of the signal fed back from the collector to the base is
These are unnecessary harmonic components, which are canceled out and the output signal is almost only the signal of the frequency to be oscillated. [Effect] Spurious radiation can be prevented with a simple configuration without mounting a shield case, and the electronic device can be made smaller and lighter.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of a high frequency oscillator circuit.

[0002]

[Prior art]

 Conventionally, in equipment equipped with a high-frequency oscillator circuit, the spurious signal (harmonic signal) is removed by passing the output signal of the high-frequency oscillator circuit 1 through a low-pass filter 2 as shown in FIG. Had taken out. As a result, even if the output signal of the high-frequency oscillator circuit 1 contains multiple harmonics 2f0 to 7f0, etc. as shown in FIG. 3 (a), it is low as shown in FIG. 3 (b). Higher-order harmonic signals are removed from the output signal of the band-pass filter 2, and the strengths of the second- and third-order harmonics are weakened.

[0003]

[Problems to be solved by the device]

 Generally, in a high frequency circuit, not only the signal is transmitted along the wiring or pattern of the circuit, but also the signal is radiated into the air from the wiring or pattern. For this reason, in the above-described conventional electronic configuration, the high-frequency oscillator circuit 1 and the low-pass filter 2 are covered with a shield case to prevent leakage of harmonics output from the high-frequency oscillator circuit 1. However, as electronic devices become smaller and lighter, it becomes very difficult to attach a shield case, which hinders the miniaturization and weight saving of electronic devices.

In view of the above problems, an object of the present invention is to provide a high frequency oscillation circuit that can reduce the emission of harmonic signals without mounting a shield case.

[0005]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a high-frequency oscillation circuit using a bipolar transistor, wherein in the high-frequency oscillation circuit, a feedback circuit for eliminating a signal of a frequency within a predetermined band having a center frequency at an oscillation target frequency is provided. We propose a high-frequency oscillator circuit connected between the base and collector of a bipolar transistor.

According to a second aspect of the present invention, there is provided a high frequency oscillation circuit using a bipolar transistor, wherein the base-collector voltage is set so that the base-collector capacitance of the bipolar transistor becomes a predetermined value or more. suggest.

[0007]

[Action]

 According to the first aspect of the present invention, the collector signal of the bipolar transistor is fed back to the base of the bipolar transistor through the feedback circuit. Here, in the bipolar transistor, the waveform of the base signal and the waveform of the emitter signal have the same phase, but the waveform of the base signal and the waveform of the collector signal have the opposite phase. Further, the frequency of the signal returned from the collector to the base is a signal having a frequency outside the predetermined band whose center frequency is the frequency to be oscillated, that is, an unnecessary harmonic component. The components are canceled out, and the output signal is almost only the signal of the frequency to be oscillated.

According to the second aspect, in the bipolar transistor, the base-collector capacitance increases substantially in proportion to the forward voltage between the base and collector. Therefore, a high-pass filter is formed between the base and collector by setting the base-collector voltage so that the base-collector capacitance of the bipolar transistor becomes a predetermined value or more. Further, in the bipolar transistor, the waveform of the base signal and the waveform of the emitter signal are in phase with each other, but the waveform of the base signal and the waveform of the collector signal are in phase with each other. The frequency of the signal fed back to the base is a signal with a frequency higher than the frequency to be oscillated, that is, unnecessary harmonic components, so these harmonic components are canceled out and the output signal is almost oscillated. Only frequency signals are available.

[0009]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a crystal oscillator circuit according to a first embodiment of the present invention. In the figure, 11 is a bipolar transistor (hereinafter referred to as a transistor) having an NPN, 12 is a crystal oscillator having an oscillation frequency f0, 13 is a variable capacitor, 14 and 15 are capacitors, and 16 to 19 are resistors. , 20 are band elimination filters (hereinafter referred to as filters).

A filter 20 is connected between the base and collector of the transistor 11, and a capacitor 14 is connected between the base and emitter. The emitter of the transistor 11 is grounded via a capacitor 15 and a resistor 19 which are connected in parallel, and the base is connected to one end of the crystal oscillator 12 and is grounded via a resistor 17. The other end of the crystal oscillator 12 is grounded via a variable capacitor 13. Furthermore, a predetermined voltage Vcc is applied to each of the base and collector of the transistor 11 via the corresponding resistors 16 and 18. Further, the band elimination filter 20 is composed of, for example, an LC filter, removes only the signal of the frequency within a predetermined band having the oscillation frequency f0 of the crystal oscillator 12 as the central frequency, and has the frequency outside this band. Pass the signal.

Next, the operation of the first embodiment having the above configuration will be described. When the voltage Vcc is applied to the crystal unit 12 through the resistor 16, the voltage across the crystal unit 12 changes in accordance with the oscillation frequency due to the piezoelectric effect, and the base voltage Vb of the transistor 11 changes. Changes. As a result, the base-emitter voltage Vbe of the transistor 11 changes and the collector current Ic changes corresponding to the voltage Vbe, so that the transistor 11 is kept in resonance with the oscillation frequency f0. That is, as shown in FIG. 4, as the base voltage Vb increases, the collector current Ic also increases, and the voltage drop in the resistors 18 and 19 increases. Therefore, when the base voltage Vb increases, the emitter voltage Ve increases and the collector voltage Vc decreases. Further, as the base voltage Vb decreases, the collector current Ic also decreases, and the voltage drop in the resistors 18 and 19 decreases. Therefore, when the base voltage Vb decreases, the emitter voltage Ve decreases, and the collector voltage Vc increases because it approaches the voltage Vcc. As a result, the signal of frequency f0 can be taken out from the collector of the transistor 11.

On the other hand, in the oscillation process, a harmonic of the oscillation frequency f0 of the crystal oscillator 12 is also generated, and this harmonic component is also superimposed on the collector current Ic to change the emitter voltage Ve and the collector voltage Vc. Here, in the first embodiment, since the band elimination filter 20 is connected between the base and collector of the transistor 11, the harmonic component in the change of the collector voltage Vc is fed back to the base.

Further, as described above, in the bipolar transistor 11, the waveform of the base voltage Vb and the waveform of the emitter voltage Ve have the same phase, but the waveform of the base voltage Vb and the waveform of the collector voltage Vc have opposite phases. Therefore, the harmonic component at the base voltage Vb and the harmonic component fed back from the collector via the band elimination filter 20 are canceled.

Therefore, it is possible to prevent harmonic components and other spurious emissions with a simple structure without mounting a shield case, and it is possible to reduce the size and weight of the electronic device.

Next, a second embodiment of the present invention will be described. FIG. 5 is a circuit diagram of a crystal oscillator circuit according to the second embodiment. In the figure, the same components as those of the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted. Further, the difference between the first embodiment and the second embodiment is that the band elimination filter 20 is removed and the base voltage Vb and collector voltage Vcb of the transistor 11 are set in order of the collector-base voltage Vcb. This is because the resistance values of the resistors 16 to 19 are set so as to be biased.

As is well known, the junction capacitance C of the pn junction depends on the voltage, and the junction capacitance C increases as the reverse bias voltage becomes lower, and the junction capacitance C further increases when a forward bias voltage is applied. Utilizing this, in the second embodiment, the resistance values of the resistors 16 to 19 are adjusted so that the junction capacitance C of the pn junction between the base and the emitter becomes a predetermined value. Vc is set.

As a result, the junction capacitance C between the base and collector operates as a high-pass filter, and the harmonic component is fed back to the base via this junction capacitance. Here, similarly to the above, in the bipolar transistor 11, the waveform of the base voltage Vb and the waveform of the emitter voltage Ve have the same phase, but the waveform of the base voltage Vb and the waveform of the collector voltage Vc have the opposite phase. The harmonic component at the base voltage Vb and the harmonic component fed back from the collector via the band elimination filter 20 are canceled.

Therefore, without mounting a shield case, it is possible to prevent harmonic components and other spurious emissions with a simple structure, and it is possible to reduce the size and weight of the electronic device.

[0020]

[Effect of device]

 As described above, according to claim 1 of the present invention, the frequency of the signal returned from the collector of the bipolar transistor to the base through the feedback circuit is outside the predetermined band whose center frequency is the frequency to be oscillated. Signal of the frequency, that is, unnecessary harmonic components, these harmonic components are canceled out, and the output signal becomes only the signal of the frequency to be oscillated.Therefore, it is easy to install without a shield case. With such a configuration, harmonic components and other spurious emissions can be prevented, and electronic devices can be made smaller and lighter.

According to claim 2, the frequency of the signal fed back from the collector to the base via the base-collector capacitance of the bipolar transistor is higher than the frequency of the oscillation target, that is, unnecessary. Since these harmonic components are canceled out and the output signal is almost only the signal of the frequency to be oscillated, there is no need to install a shield case. The spurious emission can be prevented, and the electronic device can be made smaller and lighter, which is a very excellent effect.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a crystal oscillator circuit according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional example.

FIG. 3 is a diagram for explaining the operation of a conventional example.

FIG. 4 is a diagram for explaining the operation of the first embodiment of the present invention.

FIG. 5 is a circuit diagram showing a crystal oscillator circuit according to a second embodiment of the present invention.

[Explanation of symbols]

11 ... Bipolar transistor, 12 ... Crystal oscillator, 1
3 ... Variable capacitors, 14, 15 ... Capacitors, 16-
19 ... Resistor, 20 ... Band elimination filter.

Claims (2)

[Scope of utility model registration request] 1. A high frequency oscillating circuit using a bipolar transistor, wherein a feedback circuit for erasing a signal having a frequency within a predetermined band having a center frequency of an oscillation target frequency is connected between a base and a collector of the bipolar transistor. , A high-frequency oscillator circuit characterized by the above. 2. A high frequency oscillating circuit using a bipolar transistor, wherein the base-collector voltage is set so that the base-collector capacitance of the bipolar transistor becomes a predetermined value or more.